Lab Reports

General Information

Your labs will require you do several different things: perform measurements, calculate expected values and compare to measured, derive equations, make up your own circuits. Your lab report will be the findings from these various activities. Please be very clear what exactly you're answering.

A good lab report does more than present data; it demonstrates the writer's comprehension of the concepts behind the data. Merely recording the expected and observed results is not sufficient; you should also identify how and why differences occurred, explain how they affected your experiment, and show your understanding of the principles the experiment was designed to examine. Bear in mind that a format, however helpful, cannot replace clear thinking and organized writing. You still need to organize your ideas carefully and express them coherently.

• Methods and Materials (or Equipment) can usually be a simple list, but make sure it is accurate and complete. In some cases, you can simply direct the reader to a lab manual or standard procedure: "Equipment was set up as in the manual."
  
  
• Experimental Procedure describes the process in chronological order. Using clear paragraph structure, explain all steps in the order they actually happened, not as they were supposed to happen. If your professor says you can simply state that you followed the procedure in the manual, be sure you still document occasions when you did not follow that exactly (e.g. "At step 4 we performed four repetitions instead of three, and ignored the data from the second repetition"). If you've done it right, another researcher should be able to duplicate your experiment.
  
  
• Results are usually dominated by calculations, tables and figures; however, you still need to state all significant results explicitly in verbal form, for example: Using the calculated I gives R = 0.1244 ohms.

Graphics need to be clear, easily read, and well labeled (e.g. Figure 1: Input Frequency and Capacitor Value). An important strategy for making your results effective is to draw the reader's attention to them with a sentence or two, so the reader has a focus when reading the graph.

• Discussion is the most important part of your report, because here, you show that you understand the experiment beyond the simple level of completing it. Explain. Analyse. Interpret. Some people like to think of this as the "subjective" part of the report. By that, they mean this is what is not readily observable. This part of the lab focuses on a question of understanding "What is the significance or meaning of the results?" To answer this question, use both aspects of discussion:
  
  
  • 1. Analysis What do the results indicate clearly? What have you found? Explain what you know with certainty based on your results and draw conclusions:

    Since none of the samples reacted to the Silver foil test, therefore sulfide, if present at all, does not exceed a concentration of approximately 0.025 g/l. It is therefore unlikely that the water main pipe break was the result of sulfide-induced corrosion.

    
    
  • 2. Interpretation What is the significance of the results? What ambiguities exist? What questions might we raise? Find logical explanations for problems in the data:

    Although the water samples were received on 14 August 2000, testing could not be started until 10 September 2000. It is normally desirably to test as quickly as possible after sampling in order to avoid potential sample contamination. The effect of the delay is unknown.

    More particularly, focus your discussion with strategies like these:
    • Compare expected results with those obtained.
    • If there were differences, how can you account for them? Saying "human error" implies you're incompetent. Be specific; for example, the instruments could not measure precisely,, or calculated values did not take account of other effects. Analyze experimental error.
    • Was it avoidable? Was it a result of equipment? If an experiment was within the tolerances, you can still account for the difference from the ideal. If the flaws result from the experimental design explain how the design might be improved. Explain your results in terms of theoretical issues.
    • Often undergraduate labs are intended to illustrate important physical laws, such as Kirchhoff's voltage law. Usually you will have discussed these in the introduction. In this section move from the results to the theory. How well has the theory been illustrated? Relate results to your experimental objective(s).

Lab Report Requirements

You will not be penalized if you don't produce the expected result from a lab. You will lose points if you do not try to explain why your observation differs from expectation.